Should you trust experts?

You have never personally checked that the Earth goes round the sun, or that your medicine contains what its label says. Someone told you, and you believed them. Nearly everything you know, you know that way. The question is whether that trust is good judgment or a habit you have never examined. Plato thought the answer was obvious. In the Republic he pictures a ship whose sailors fight over the helm and flatter its half-deaf owner while mocking the one man who can actually navigate as a useless stargazer. Let those who know how to steer, steer. His critics have pointed out ever since that this leaves the crew's problem untouched: how do you tell the real navigator from the most confident claimant? History offers warnings in both directions. In 1847 Ignaz Semmelweis cut deaths on his Vienna maternity ward dramatically by making doctors wash their hands in a chlorine solution; much of the medical establishment brushed him off, and he died in an asylum. Molière spent a career mocking doctors who hid their ignorance behind Latin. In 1673, playing a hypochondriac in his own comedy The Imaginary Invalid, he was taken ill on stage and died that night. The philosopher Alvin Goldman stated the modern problem plainly in 2001. Someone without expertise usually can't weigh the evidence, so when experts disagree the novice has to weigh the experts instead: their track records, their interests, how many of their peers agree, how well they argue. None of these is foolproof. A machine that answers anything raises the stakes, because it often sounds just as sure when it is wrong. Name one expert you trust completely. What, honestly, is that trust based on?